1. Field of the Invention
The present invention relates to improvement of the display of a liquid crystal device using a polymerizable material that can be polymerized by light, heat, or a combination thereof. Such liquid crystal display devices are used in notebook personal computers, TV sets, portable TV sets, monitors, projectors, etc.
2. Description of the Related Art
In recent years, with the emergence of MVA (Multi-domain Vertical Alignment), IPS (in-plane switching) and other technologies, the viewing-angle characteristics of liquid crystals have been greatly improved. However, with respect to brightness, liquid crystal displays are still inferior to CRTs, and improvements in brightness are desired. As means for improving brightness, increase in the numerical aperture of the liquid crystal panel, or increase in the brightness of the backlight are known among other methods.
In particular, control of the liquid crystal alignment is crucial to improvement of the numerical aperture. In general, as means of controlling the alignment of liquid crystals, the provision of protrusions, control of electrode slits, formation of a cured resin or other polymers that regulate the liquid crystal alignment and other similar methods are known. Of these, the formation of a cured resin or other polymers to regulate the liquid crystal alignment is the most promising for maximizing the numerical aperture.
In the technology to create this polymer, a composition comprising a polymerizable compound such as a monomer and oligomer as well as a liquid crystal is injected into the gap between two parallel substrates on which are formed a pair of electrodes, the polymerizable compound is polymerized by applying light (usually: ultraviolet) radiation or heat processing with a voltage applied to the liquid crystal, and as a result the liquid crystal molecules are endowed with a pretilt angle (see for example Japanese Unexamined Patent Application Publication No. 2003-149647, scope of claims). Cross-linking polymerization often contributes to this polymerization, and often the result is a cured resin having a structure in which all or a portion of the polymer molecules are cross-linked.
However, this technology has the problem that display irregularities occur, as shown in FIG. 1. FIG. 1 is a schematic diagram as seen from the direction of observation of the screen of a liquid crystal panel 1. In the halftone display of FIG. 1, the most screen portion 3 of the liquid crystal display panel 1 displays normal halftones, but in the left-hand portion 4 of FIG. 1 the display is whitish. This portion 4 appears on the side opposite to the side of the panel screen where an injection aperture 2 used to inject the liquid crystal into the liquid crystal panel 1 is located.